The audiences are the main constitutional requirement that the president must observe before he may announce a decision on a new prime minister.


The right-of-centre government that took office in the wake of the 4 October general election, having lost its majority, was last week forced to resign after parliament rejected its programme. The Socialist Party, which came second in the election, has reached agreements with three other left-of-centre parties that it says make viable an alternative government.


There is no deadline for the president's decision and he has the option of asking the incumbent, Pedro Passos Coelho, to stay on in a caretaker capacity.


The president's audiences with the Social Democratic Party, Socialist Party, Popular Party, Left Bloc, Communist Party, Greens and People-Animals-Nature are to take place throughout the day on Friday.


According to the source, the president is on Thursday to receive a number of economists with "knowledge of the economic and national reality".


That follows Wednesday's series of audiences with the heads of the country's leading banks. Last week, the president received business and employer confederations and trade union leaders.